In the manufacture of semiconductor or microelectronic circuits or so-called packages, several processes may be carried out by machine vision systems, including inspection of the package electrical leads to determine if any leads are out of place or damaged, or inspection of the package for certain markings placed thereon. Machine vision systems have been developed to carry out these tasks in view of the need to automate the manufacturing process for semiconductor packages, taking into consideration the substantial number of such packages which are produced. Moreover, many inspection and marking systems for processing semiconductor packages are adapted to handle various configurations of packages having different shapes, lead configurations and light reflecting characteristics.
In this last mentioned regard, a lighting system which is set up for the proper contrast or image for one type of package usually requires adjustment for a different type of package. Still further, packages of essentially the same type or configuration may be fabricated of different materials which have at least slightly different light reflectivity characteristics. Therefore, a vision apparatus adapted for inspecting a particular type of semiconductor package may not function properly if slight changes in materials used for the packages or any changes in the light reflectivity of the package occurs which will change the contrast and the quality of the image captured by the inspection or vision apparatus.
Accordingly, there has been a need for a lighting system for machine vision apparatus which is adaptable to vary the light intensity on various parts of an article or device being inspected, such as various types of integrated circuit or semiconductor packages, to enhance the image of the package, as viewed by a vision apparatus. Moreover, there has also been a need for a system which will automatically adjust the lighting imposed on different types of articles being inspected or otherwise viewed by a vision apparatus to enhance the accuracy of an inspection process or any process which requires machine vision of an article, such as an electronic circuit or semiconductor package. Still further, since the intensity and pattern of the lighting imposed on different articles being inspected is important, it is also important to provide for monitoring the failure of any part of the lighting system so that improper lighting and inspection of articles being illuminated by the system is not experienced. It is to accomplish the desiderata mentioned above and overcome problems associated with prior art apparatus that the present invention has been developed.